The militant Islamic State poses an "imminent threat" to the US and may take years to defeat, defence secretary Chuck Hagel has said.
"They are an imminent threat to every interest we have, whether it's in Iraq or anywhere else," he said during a Pentagon news conference.
The beheading by Islamic State of American journalist James Foley, shown in a graphic video released this week, has drawn fresh attention and international condemnation to the terrorist group that has seized a swath of Syria and Iraq in its quest to create a Sunni caliphate.
Islamic State "is as sophisticated and well-funded as any group that we have seen," Mr Hagel said. "They're beyond just a terrorist group. They marry ideology, a sophistication of strategic and tactical military prowess. They are tremendously well-funded."
The US intelligence community thinks Islamic State has an incentive to conduct a major terrorist strike against US or European targets, in part to further assert itself as the true leader of radical Islam, according to five US intelligence officials who briefed reporters last week on condition of anonymity to discuss intelligence assessments.
Mr Hagel said US airstrikes in Iraq “have stalled” the group’s “momentum and enabled Iraqi and Kurdish forces to regain their footing and take the initiative.”
Appearing alongside Hagel, Army General Martin Dempsey, chairman of the Joint Chiefs of Staff, said Islamic State "will only truly be defeated when it's rejected by the 20 million disenfranchised Sunni that happen to reside between Damascus and Baghdad."
Gen Dempsey said that means the group also will have to be taken on in Syria, where the Obama administration opposes both the group and the regime of president Bashar al-Assad that it’s working to topple.
The administration backs what it calls moderate opposition forces that have been overshadowed by militants. “Can they be defeated without addressing that part of their organization which resides in Syria?” Gen Dempsey said.
“The answer is no. That will have to be addressed on both sides of what is essentially at this point a nonexistent border.”
President Barack Obama has pressed for a more "inclusive" national government in Iraq to win over Sunnis who considered themselves disenfranchised under the Shiite-led government of departing prime minister Nouri al-Maliki.
Mr Obama has said the US won’t put combat troops on the ground in Iraq and that limited targets for airstrikes would be expanded only after an inclusive government is in place.
Gen Dempsey said Islamic State, which the US intelligence community says numbers about 10,000, poses a more immediate threat to Europe than to the US.
“The immediacy is in the number of Europeans and other nationalities who have come to the region to become part of that ideology, and those folks can go home at some point,” Gen Dempsey said.
US and UK authorities are investigating the video showing Foley’s murder that’s narrated by a man with a British accent. The terrorists “can be contained” in Iraq on the battlefield although “not in perpetuity,” Gen Dempsey said. “This is an organisation that has an apocalyptic, ‘end-of-days’ strategic vision and which will eventually have to be defeated.”
The methods for attacking Islamic State will require “all of the tools of national power - diplomatic, economic, information, military,” he added.
Bloomberg